How to make a real mirror on blender with cycle engine
I felt this was a good question, so I've added an answer for future users. Also, maybe some of my info will add to what you've already discovered.

To make a mirror in cycles, use a glass shader (for obvious reasons), a fresnel shader (to ensure that the light hitting the mirror is complimented by the angle at which it’s shining, as described here), and a glossy shader at low roughness (which is similar to a glass shader but will bend light in a slightly different way, adding to the realism). These can all be easily found by hitting Spacebar and typing the node name. The base object is a simple mesh plane.



I’ve added two glass shaders with 2 different colours, for additional realism.



Be sure to add another coloured plane behind the mirror, so the light rays stop at the mirror glass (and are then reflected) instead of passing right through.